Point-of-care (POC) in vitro diagnostics tests (IVDT) have traditionally had two major categories, nucleic acid amplification tests (NAAT) or immunoassay-based tests. The former directly detects the pathogen's DNA or RNA, while the latter detects antibodies or antigens generated by the immune system response to the pathogen.
Current POC diagnostic immunoassays lack the high sensitivity and specificity of nucleic acid amplification methods. This becomes more pronounced during the initial stages of infection, often within 168 hours. Taking the case of Dengue virus in whole blood, immunoglobulin M (IgM) and immunoglobulin G (IgG) remain undetectable in the majority of patients until 5 and 10 days post-infection, respectively, whereas nucleic acid can be found as early as 0 to 7 days. Moreover, many immunoassay tests are unable to detect infectious agents until 3 months after the initial onset of the infection. This delay is due to the time it takes for the body's immune system to respond to an infection.
POC diagnostic assays developed utilizing NAATs have very high sensitivities and specificities, matching those of currently accepted laboratory tests. The primary mechanism of NAAT based systems is to directly detect an infectious agent's nucleic acid, lending to the test's ability to detect diseases within the first few days of the onset of infection. In addition, by careful primer design, NAATs also have the ability to have very high specificity and sensitivity compared to immunoassay based testing. The largest drawback of NAATs compared to immunoassay-based tests is the complicated equipment and/or processes required to prepare a sample for testing.